1. Field of the Invention
The present invention generally relates to an image-pickup semiconductor device and, more particularly, to an image-pickup semiconductor device packaged with a semiconductor element having a light-receiving element and a lens for picking up an image.
Recently, a cellular phone and a handy PC (a portable personal computer) with a miniature camera incorporated therein have been developed. A cellular phone equipped with a miniature camera, for example, picks an image of the speaker by the miniature camera, converts the image into image data, and transmits the image data to another speaker on the other side of the line. Such a miniature camera like this generally comprises a C-MOS sensor and a lens.
Such a cellular phone and a handy PC are being further miniaturized, and accordingly, the miniature camera used in these apparatus is also required to be smaller. To satisfy the needs like this, a semiconductor device package combining a lens and a C-MOS sensor has been developed.
2. Description of the Related Art
Japanese Laid-Open Pat. App. No. 11-17997 discloses a semiconductor device package having a structure combining a lens for picking an image and a semiconductor chip having a C-MOS sensor. In this semiconductor device package, the semiconductor chip having the C-MOS sensor is mounted on a rigid printed substrate by wire bonding, with a light-receiving surface of the semiconductor chip facing upward. The lens is fixed relative to the printed substrate so as to be placed at a predetermined position above the light-receiving surface of the semiconductor chip. Thus, the conventional semiconductor device package as a miniature camera disclosed in Japanese Laid-Open Pat. App. No. 11-17997 comprises the semiconductor chip mounted on the substrate; and the lens placed above the semiconductor chip.
The above-mentioned semiconductor device package has the following disadvantages originating from the structure thereof.
1) In manufacturing the semiconductor chip having a light-receiving element, the back surface of the semiconductor chip is grinded by a polisher so as to reduce the thickness of the semiconductor chip. For this reason, semiconductor chips on different wafers have various thicknesses. Although a range of the variation in thickness is normally about xc2x115 xcexcm, a tolerable range thereof is about xc2x130 xcexcm. The varied thickness of the semiconductor chip changes the distance between the light-receiving surface of the semiconductor chip and the lens. In other words, since the lens is placed at a predetermined distance from the surface of the printed substrate, and the light-receiving surface of the semiconductor chip is at a distance equivalent to the thickness of the semiconductor chip from the surface of the printed substrate, the light-receiving surface comes closer to the lens as the thickness of the semiconductor chip is increased, and goes farther from the lens as the thickness of the semiconductor chip is reduced.
The distance between the lens and the light-receiving surface of the semiconductor chip is arranged to be equal to a focal distance of the lens so that light rays transmitting through the lens form an accurate image on the light-receiving surface. Therefore, the above-mentioned varied distance between the lens and the light-receiving surface of the semiconductor chip arouses disadvantages, such as an image out of focus.
2) In mounting the semiconductor chip on the printed substrate, the semiconductor chip is applied and fixed to the surface of the printed substrate by using a dice-applying machine. The dice-applying machine holds the semiconductor chip by sucking the surface (on which the light-receiving element is formed) of the semiconductor chip, and then conveys the semiconductor chip to the printed substrate and places the semiconductor chip thereon. Therefore, the surface of the semiconductor chip is covered by a suction device, preventing a visual recognition of the surface of the semiconductor chip on which the light-receiving element is formed. Instead, the external shape of the semiconductor chip is recognized visually as a basis in adjusting the location of the semiconductor chip on the printed substrate. However, the light-receiving surface and the external shape of the semiconductor chip do not necessarily have a consistent positional relation. In other words, the semiconductor chip, which is formed by dicing a wafer into individual semiconductor chips, has an inconsistent external shape depending on the severing position in dicing. Thereby, the relative position of the light-receiving surface of the semiconductor chip to the external shape of the semiconductor chip is not consistent. Therefore, there are cases where a focal point of the lens does not accurately match the center of the light-receiving surface.
3) Since the semiconductor chip is mounted on the printed substrate by wire bonding, pads for wire bonding have to be provided around the semiconductor chip. Accordingly, the printed substrate needs to have a space to accommodate these pads for wire bonding. This impedes a miniaturization of the semiconductor device package.
4) The semiconductor device package substantially requires a thickness equivalent to a total of the focal distance of the lens and the thickness of the semiconductor chip. However, since the above-mentioned conventional semiconductor device package has the printed substrate placed on the opposite side of the semiconductor chip to the lens, the semiconductor device package actually has a thickness equivalent to a total of the focal distance of the lens and the thickness of the semiconductor chip plus the thickness of the printed substrate. Thus, the thickness of the semiconductor device package is increased by the thickness of the printed substrate.
5) The printed substrate is formed of rigid materials, such as ceramics, or a glass epoxy. Therefore, the printed substrate is not flexible, causing a disadvantage that the semiconductor device package cannot be placed freely when being incorporated into an apparatus. Specifically, there is a restriction that the semiconductor device package has to be directly mounted on a main substrate of a cellular phone or a handy PC, or a flexible wiring substrate has to be provided between the main substrate and the semiconductor device package, in order that the semiconductor device package forming a miniature camera is electrically connected to the main substrate of the cellular phone or the handy PC. This restriction reduces a degree of freedom in designing a body of a cellular phone or a handy PC.
It is a general object of the present invention to provide an improved and useful image-pickup semiconductor device packaged with a semiconductor element having a light-receiving element and a lens for picking up an image in which device the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide a packaged image-pickup semiconductor device having a smaller thickness and area than a conventional image-pickup semiconductor device package.
In order to achieve the above-mentioned objects, there is provided according to one aspect of the present invention a semiconductor device for picking up an image, the device comprising:
a lens-mounting unit provided with a lens for picking up an image;
a semiconductor chip having a light-receiving element formed on a circuit-forming surface thereof, the light-receiving element converting light from the lens into an image signal;
a flexible substrate provided between the lens-mounting unit and the semiconductor chip so as to supply the image signal to an external circuit; and
a shading plate blocking light transmitting through the flexible substrate toward the semiconductor chip so as to substantially remove an influence of the light on the light-receiving element.
According to the present invention, the substrate on which the semiconductor chip is mounted is placed between the circuit-forming surface of the semiconductor chip and the lens. Thereby, the thickness of the substrate can be included in the distance between the lens and the light receiving-element formed on the circuit-forming surface of the semiconductor chip, i.e., the focal distance of the lens, without increasing the focal distance. Accordingly, the thickness of the image-pickup semiconductor device is substantially equal to a total of the focal distance of the lens and the thickness of the semiconductor chip. In other words, the thickness of the substrate does not add to the thickness of the entire image-pickup semiconductor device, reducing the thickness thereof to that extent. Additionally, although the flexible substrate has a property of transmitting light, the shading plate can block the light transmitting through the substrate so as to substantially exclude an influence of the light over the light-receiving element. This prevents a deterioration of the image.
Additionally, in the image-pickup semiconductor device according to the present invention, the semiconductor chip may be mounted on the flexible substrate with the circuit-forming surface facing the flexible substrate so that the light-receiving element opposes the lens through an opening formed in the flexible substrate.
According to the present invention, since an opening is formed in the substrate, the light-receiving element formed on the circuit-forming surface can be placed opposite to the lens provided on the other side of the substrate through the opening, even in a case where the semiconductor chip is mounted on the substrate by flip chip mounting, etc. In addition, in mounting the semiconductor chip on the substrate, the surface of the semiconductor chip opposite to the circuit-forming surface can be supported, the semiconductor chip can be mounted while the circuit-forming surface being visually recognized. Thereby, the semiconductor chip can be mounted on the substrate with a high positional precision.
Additionally, in the image-pickup semiconductor device according to the present invention, the lens-mounting unit may have a locating pin, and the flexible substrate may have a locating hole so that, in a state where the locating pin is inserted into the locating hole, the lens-mounting unit is fixed on a surface of the flexible substrate by an adhesive, the surface being opposite to a surface on which the semiconductor chip is mounted.
According to the present invention, by inserting the locating pin of the lens-mounting unit into the locating hole formed in the substrate, the lens-mounting unit can be mounted on the substrate with a high positional precision. Since the semiconductor chip can also be mounted on the substrate with a high positional precision, as mentioned above, the lens and the semiconductor chip can be assembled with a high positional precision.
Additionally, in the image-pickup semiconductor device according to the present invention, the shading plate may extend from the lens-mounting unit toward the semiconductor chip in an opening formed in the flexible substrate.
According to the present invention, the shading plate can be formed as a part of the lens-mounting unit, easily achieving the light-blocking effect for the light-receiving element.
Additionally, in the image-pickup semiconductor device according to the present invention, the shading plate may be formed of an elastic material, an end of the shading plate adjoining the circuit-forming surface.
According to the present invention, the shading plate adjoins the circuit-forming surface of the semiconductor chip so that the shading plate completely blocks the light transmitting through the substrate. Additionally, when the shading plate adjoins the circuit-forming surface, the shading plate undergoes an elastic deformation so as not to harm the circuit-forming surface.
Additionally, in the image-pickup semiconductor device according to the present invention, the shading plate may be formed as a part of the lens-mounting unit, an end of the shading plate being fixed on the circuit-forming surface by an adhesive.
According to the present invention, the lens-mounting unit can be fixed directly on the circuit-forming surface of the semiconductor chip via the shading plate that is a part of the lens-mounting unit. This excludes an influence on the light-receiving element by the light transmitting through the substrate, and also excludes a possibility that a variation in thickness of the substrate influences the distance between the lens and the light-receiving element.
Additionally, in the image-pickup semiconductor device according to the present invention, the lens-mounting unit may have a diaphragm defining an opening functioning as an aperture for the lens, an end of the diaphragm being an inclined surface inclined by a predetermined angle from an optical axis of the lens.
According to the present invention, light rays can be kept from reflecting on the end surface of the diaphragm and then entering the light-receiving element. This avoids a deterioration of the image.
Additionally, in the image-pickup semiconductor device according to the present invention, the flexible substrate may have a wiring outlet to be connected to the external circuit, an electric component being mounted on the wiring outlet.
According to the present invention, an electric component can be mounted on the wiring outlet in an effective utilization of space so as to increase a packaging density of the image-pickup semiconductor device.
In order to achieve the above-mentioned objects, there is also provided according to another aspect of the present invention a semiconductor device for picking up an image, the device having a lens-mounting unit provided with a lens for picking up an image; a semiconductor chip having a light-receiving element formed thereon, the light-receiving element converting light from the lens into an image signal; and a substrate having the semiconductor chip mounted thereon,
wherein the lens-mounting unit has an upper portion provided with the lens; and an lower portion fixed on the substrate, the upper portion having a structure capable of moving relative to the lower portion in a direction approaching the substrate and in a direction departing from the substrate so that a distance between the lens and the semiconductor chip is variable.
According to the present invention, the distance between the lens and the semiconductor chip can be varied so as to adjust the focus of the lens to the light-receiving element in any case. Thereby, an image in focus can always be achieved.
Additionally, the image-pickup semiconductor device according to the present invention may further comprise a remove-stopper mechanism preventing the upper portion from being removed from the lower portion when the upper portion moves in the direction departing from the substrate.
According to the present invention, the remove-stopper mechanism prevents a vibration of the image-pickup semiconductor device, for example, from causing the upper portion to be detached from the lower portion.